Reduction of Hysteresis in Hybrid Perovskite Transistors by Solvent-Controlled Growth (original) (raw)
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Effect of 6R and 12R lead iodide polytypes on MAPbI3 perovskite device performance
Journal of Materials Science: Materials in Electronics, 2018
We compare the structural, morphological and electrical properties of two variants of the ITO/ZnO/CH 3 NH 3 PbI 3 /PDOT:PSS/ Au thin film perovskite device made using two structurally different forms of lead iodide. The first device was based on a commercially sourced, common 12R polytype. The second device uses the rarer 6R polytype, as recently synthesized by the authors from depleted sealed lead acid batteries. XRD measurements confirmed the presence of the orthorhombic 6R polytype and the tetragonal 12R polytype. Raman spectroscopy confirmed the presence of all organic-inorganic halide materials. Current-voltage measurements for both samples show good rectifying behavior of the resulting heterogeneous Schottky diodes. The ideality factors and barrier heights were found to be 4.07/4.09 and 0.500/0.496 eV for the 6R/12R polytypes, respectively. The 6R polytype devices appeared to show improved I-V characteristics in comparison to the 12R polytype, thus suggesting an avenue to enhance the performance of MAPbX3 prevoskite devices.
Single crystal hybrid perovskite field-effect transistors
Nature Communications
The fields of photovoltaics, photodetection and light emission have seen tremendous activity in recent years with the advent of hybrid organic-inorganic perovskites. Yet, there have been far fewer reports of perovskite-based field-effect transistors. The lateral and interfacial transport requirements of transistors make them particularly vulnerable to surface contamination and defects rife in polycrystalline films and bulk single crystals. Here, we demonstrate a spatially-confined inverse temperature crystallization strategy which synthesizes micrometre-thin single crystals of methylammonium lead halide perovskites MAPbX 3 (X = Cl, Br, I) with sub-nanometer surface roughness and very low surface contamination. These benefit the integration of MAPbX 3 crystals into ambipolar transistors and yield record, room-temperature field-effect mobility up to 4.7 and 1.5 cm 2 V −1 s −1 in p and n channel devices respectively, with 10 4 to 10 5 on-off ratio and low turn-on voltages. This work paves the way for integrating hybrid perovskite crystals into printed, flexible and transparent electronics.
Science Advances
Despite sustained research, application of lead halide perovskites in field-effect transistors (FETs) has substantial concerns in terms of operational instabilities and hysteresis effects which are linked to its ionic nature. Here, we investigate the mechanism behind these instabilities and demonstrate an effective route to suppress them to realize high-performance perovskite FETs with low hysteresis, high threshold voltage stability (ΔVt < 2 V over 10 hours of continuous operation), and high mobility values >1 cm2/V·s at room temperature. We show that multiple cation incorporation using strain-relieving cations like Cs and cations such as Rb, which act as passivation/crystallization modifying agents, is an effective strategy for reducing vacancy concentration and ion migration in perovskite FETs. Furthermore, we demonstrate that treatment of perovskite films with positive azeotrope solvents that act as Lewis bases (acids) enables a further reduction in defect density and subs...
Coatings
Controlling the crystallinity, homogeneity, and surface morphology is an efficient method of enhancing the perovskite layer. These improvements contribute toward the optimization of perovskite film morphology for its use in high-performance photovoltaic applications. Here, different solvents will be used in order to process the perovskite precursor, to improve the interfacial contacts through generating a smooth film and uniform crystal domains with large grains. The effect that the solvent has on the optical and structural properties of spin-coated methyl ammonium lead iodide (MAPbI3) perovskite thin films prepared using a single-step method was systematically investigated. The spin-coating parameters and precursor concentrations of MAI and PbI2 were optimized to produce uniform thin films using the different solvents N, N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and γ-butyrolactone (GBL). The effect that the solvent has on the morphology of the MAPbI3 films was examined...
Frontiers in Energy Research, 2022
This work reported the successive incorporation of tetrabutylammonium (TBA) into Methylammonium lead Iodide (MAPbI3) perovskite. The thin films were characterized by X-Ray diffraction (XRD), Scanning electron microscopy (SEM), Transmittance electron microscopy (TEM), Atomic force microscopy (AFM), and UV-Visible spectroscopy. It was shown that introducing TBA increases the crystallinity, grain size, surface morphology without pin-hole, and roughness of the MAPbI3 thin films. Moreover, the MA(1-X)TBAX PbI3 thin film shows better stability in a relative humidity of ∼60% after 15 days than the pure MAPbI3 thin film. The obtained results are hoped to be helpful for stability and improvement of the performance of the MAPbI3 thin films by doping TBA cations under ambient conditions.
Scientific Reports, 2018
Solution-based methods represent the most widespread approach used to deposit hybrid organic-inorganic perovskite films for low-cost but efficient solar cells. However, solution-process techniques offer limited control over film morphology and crystallinity, and most importantly do not allow sequential film deposition to produce perovskite-perovskite heterostructures. Here the successful deposition of CH3NH3PbI3 (MAPI) thin films by RF-magnetron sputtering is reported, an industry-tested method to grow large area devices with precisely controlled stoichiometry. MAPI films are grown starting from a single-target made of CH3NH3I (MAI) and PbI2. Films are single-phase, with a barely detectable content of unreacted PbI2, full surface coverage and thickness ranging from less than 200 nm to more than 3 μm. Light absorption and emission properties of the deposited films are comparable to as-grown solution-processed MAPI films. The development of vapor-phase deposition methods is of interes...
Stability Improvement of Methylammonium Lead Iodide Perovskite Thin Films by Bismuth Doping
JOM
Perovskites have been in the spotlight in the field of solar cells due to their high efficiency and their low cost of materials and fabrication processes. Perovskite solar cells (PSCs) have shown an efficiency of up to 25%. Nevertheless, PSCs have some drawbacks such as rapid degradation in ambient conditions. To improve PSC stability, lead is usually replaced with bismuth. In this article, we report the results when doping the methylammonium lead iodide (CH3NH3)PbI3, aka MAPbI3, with different bismuth quantities. The incorporation of bismuth into the lattice leads to a remarkable change in optoelectronics and morphological structure. Substituting lead atoms with 2% bismuth improves some characteristics of MAPbI3 layers, such as removing pinholes and increasing crystallite size and optical absorption. Furthermore, bismuth doping improves the stability of pure MAPbI3 layers, which after 4 weeks exhibits higher degradation compared to bismuth-doped MAPbI3 samples, which remain stable ...
Transformation from crystalline precursor to perovskite in PbCl2-derived MAPbI3
Nature Communications
Understanding the formation chemistry of metal halide perovskites is key to optimizing processing conditions and realizing enhanced optoelectronic properties. Here, we reveal the structure of the crystalline precursor in the formation of methylammonium lead iodide (MAPbI 3) from the single-step deposition of lead chloride and three equivalents of methylammonium iodide (PbCl 2 + 3MAI) (MA = CH 3 NH 3). The as-spun film consists of crystalline MA 2 PbI 3 Cl, which is composed of one-dimensional chains of lead halide octahedra, coexisting with disordered MACl. We show that the transformation of precursor into perovskite is not favored in the presence of MACl, and thus the gradual evaporation of MACl acts as a self-regulating mechanism to slow the conversion. We propose the stable precursor phase enables dense film coverage and the slow transformation may lead to improved crystal quality. This enhanced chemical understanding is paramount for the rational control of film deposition and the fabrication of superior optoelectronic devices.
ACS Applied Energy Materials
Scalable methods for deposition of lead halide perovskite thin films are required to enable commercialization of the highly promising perovskite photovoltaics. Here, we have developed a slot-die coating process under ambient conditions for methylammonium lead iodide (MAPbI 3) perovskite on heated substrates (about 90°C on the substrate surface). Dense, highly crystalline perovskite films with large grains (100−200 μm) were obtained by careful adjustment of the deposition parameters, using solutions that are similar but more dilute than those used in typical spin-coating procedures. Without any further after treatments, such as antisolvent treatment or vapor annealing, we achieved power conversion efficiencies up of 14.5% for devices with the following structure: conducting tin oxide glass (FTO)/TiO 2 /MAPbI 3 /spiro-MeOTAD/Au. The performance was limited by the significant roughness of the deposited films, resulting from the hot-casting method, and the relatively high deposition temperature, which led to a defect-rich surface due to loss of MAI.